JP2007253308A - Manufacturing method for polishing tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a smooth polished surface in processing of an electronic device formed by various materials having different hardnesses, and to satisfy a specific characteristic required by the device. <P>SOLUTION: A polishing tool is manufactured through a substrate polishing process for smoothing the surface of a substrate, the process for forming a polishing grain layer used for polishing the surface of the electronic device on the substrate, and a surface processing process for making polishing grains project on the surface of the polishing grain layer. Thus, a smooth polishing of the device can be obtained so that the surface of the polishing tool and a polished section of the device are brought into contact with each other and slid with each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a polishing tool corresponding to a semiconductor device such as logic or DRAM, a magnetic head for a magnetic disk device, or the like.

  For example, in a magnetic disk device, it is desired to improve the surface recording density. For that purpose, it is necessary to further reduce the flying height of the magnetic head from the current magnetic recording medium to about 10 nm. In order to realize the reduction of the flying height, it is indispensable to process the slider surface (floating surface) of the magnetic head arranged to face the rotating magnetic recording medium with higher accuracy.

In general, the magnetic head is manufactured as follows. That _is, the Al ₂ O 3 -TiC (alumina titanium carbide) or the like of the rigid substrate, _Al 2 _{O 3} (alumina, thickness 2 to 10 [mu] m) as an insulating film to form a shield layer, a gap layer, magnetoresistive A magnetic element portion (GMR element, CPP-GMR element, TMR element) made of a film or the like, a lower magnetic pole, an upper magnetic pole, and a protective film (alumina layer) are sequentially laminated. The above structure is formed on a 5-inch size substrate by a thin film process using lithography.

  Thereafter, the substrate is cut into strips having a length of 2 inches using a diamond grindstone. Then, after removing the distortion after cutting using a method such as double-sided lapping, a magnetic head that faces the magnetic recording medium by polishing the surface orthogonal to the structure laminated on the substrate with high accuracy The slider surface (floating surface) is formed. Then, small pieces including individual magnetic element portions are cut out from the strip pieces to complete the magnetic head.

  By the way, in the above-described polishing method for strip pieces, the strip pieces adhered to the polishing jig are pressed and slid while dropping a lapping liquid containing abrasive grains such as diamond on a rotating soft metal base plate. Is used. As polishing conditions, when a polishing jig with a strip attached to a rotating platen is rotated in a self-revolving manner, the strip is shaken in a direction perpendicular to or parallel to the rotation direction of the platen. It may be moved.

  By the way, as a manufacturing method of a polishing tool used when polishing an electronic device such as a magnetic head in the above-described method, a method described in Patent Document 1 or Patent Document 2 is general. That is, a relatively soft metal made of a tin-based alloy or the like is used as the material of the polishing surface plate, and the surface accuracy of the surface must be finished with extremely high precision by machining. Then, in order to facilitate the discharge of sludge, polishing liquid, lubricating liquid, etc. generated during the polishing process, the surface of the polishing platen is subjected to fine groove processing (width: 10 μm, depth: μm) like an analog record board, for example. It has been subjected.

  Fixed abrasive grains such as diamond abrasive grains are provided on the surface of the polishing surface plate thus obtained. While a slurry liquid containing diamond abrasive grains having a particle diameter of about 100 nm is dropped through a slurry supply tube, a ceramic ring (correcting ring) having a weight of about 10 kg is revolved. Then, fixed abrasive grains such as diamond abrasive grains are pushed into the surface plate by the correction ring.

  At this time, since the material of the surface plate is soft, the abrasive grains pushed in by the plastic deformation are held in place as they are. Fixed abrasive grains such as diamond abrasive grains embedded in the surface of the surface plate are fixed in a state where a part thereof is exposed on the surface. Then, the loose abrasive grains or loose abrasive grains in an insufficiently embedded state are completely eliminated using a cleaning liquid containing a surfactant.

  In semiconductor devices (LSIs), so-called CMP (Chemical Mechanical Polishing) technology is used for planarization of interlayer insulating films and metal wiring formation processes. Specifically, as members such as tools used for polishing, A polishing pad having a laminated structure is used.

  The material is formed from a polyurethane material having a fine foam structure, and polishing is performed while supplying a slurry in which silica abrasive grains or alumina abrasive grains having a particle diameter of about 30 to 100 nm are dispersed on the surface of this polishing pad. Is going.

Japanese Patent Laid-Open No. 10-296620 Japanese Patent Laid-Open No. 2002-331452

  However, in such electronic devices such as semiconductors and magnetic heads, the surface to be polished is often composed of a plurality of materials. For example, in a magnetic head, the members constituting the strips described above, that is, the substrate, the insulating film, the magnetic element portion, the protective film, etc. have different mechanical hardness. It is extremely difficult to polish like this.

  Furthermore, in recent years, with the refinement of the GMR element structure as a reproducing element, the phenomenon that the resistance of the element is weakened during the manufacturing process has become obvious, and in addition to electrical damage such as electrostatic breakdown, the surface after machining such as polishing The effect of damage on the layer is also increasing. There is a demand for a surface processing method for reducing damage during such device surface processing and efficiently manufacturing a high-quality device.

  An object of the present invention is to provide a method for manufacturing a polishing tool that reduces the roughness of the device surface and is less damaged by processing in a method for manufacturing an electronic device such as a semiconductor device or a magnetic head made of a composite material. is there.

  A substrate polishing step for smoothing the substrate surface; a step of forming a polishing abrasive layer for polishing the surface of the electronic device on the substrate; and a method for causing abrasive grains to protrude from the surface of the abrasive layer. A polishing tool is produced through a surface treatment process. At this time, the abrasive layer forming step forms an elastic region on the substrate using the first plasma covering the surface of the substrate, and then further supplies the first plasma supplied with nanoparticles to the elastic region. By supplying, an abrasive grain region is formed.

The first plasma described above is sputter plasma using a material selected from C, Si, SiO ₂ , Sn and Sn-based alloys, Al, and Cu, and the nano-particles introduced into the plasma have a diameter of Is effective, diamond or SiO _{2 of} about 10 to 50 nm. Note that the nano-particles described above are negatively charged by the first plasma.

  According to the present invention, an electronic device to be processed using the above-described manufacturing method, for example, an air bearing surface of a magnetic head made of a different material is brought into contact with and slid. As a result, the air bearing surface is polished extremely smoothly. As a result, it can greatly contribute to the improvement of the flying characteristics and magnetic characteristics of the magnetic head.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, a description will be given using a processing example of a magnetic head which is one of electronic devices.
As a material used in the magnetic head, generally, Al ₂ O ₃ —TiC (alumina / titanium / carbite) is used as a material for a substrate, and Al ₂ O ₃ (alumina) is used as a material for an insulating film and a protective film. However, a composite material made of a soft magnetic metal such as permalloy is used for the shield film and the magnetic pole, respectively. The Vickers hardness of these materials is about 2000 Hv for Al ₂ O ₃ —TiC (alumina titanium carbide), about 1000 Hv for Al ₂ O ₃ (alumina), and about 200 Hv for Permalloy.

  As a polishing method for forming a magnetic head air bearing surface having such a configuration, for example, a strip-shaped row bar in which a plurality of magnetic heads that are workpieces are arranged in a row is used as a workpiece, and the polishing liquid is supplied in a rotated state. There are a method of polishing while rotating the workpiece on the surface plate, and a method of polishing while rotating the workpiece on the surface plate.

  When the surface of the magnetic head is polished using such a well-known polishing method, the surface of the polished magnetic head is uneven due to the difference in the polishing rate caused by the difference in material characteristics of each part in the magnetic element part. appear. Furthermore, since the magnetic element made of permalloy has a small hardness, scratches may be formed by polishing.

The cause of such a scratch will be described.
In the polishing of the air bearing surface of the magnetic head, processing with a small actual cutting amount is performed by the action of abrasive grains (fixed abrasive grains) held on a soft metal polishing surface plate, and the smooth device surface is small in processing steps. Is considered to be obtained. However, the abrasive grains are merely mechanically held on the surface of a surface plate made of a soft metal by plastic deformation of the metal. For this reason, during polishing, the abrasive grains fall off from the surface of the surface plate to form rolling abrasive grains, and this causes an effect.

  Furthermore, in order to continue smoothing the magnetic head surface and reducing damage in the future, generally smaller abrasive grains will be used. However, as the abrasive grain size decreases, the abrasive grains are fixed to the surface plate. It is predicted that the preparation of the tool becomes difficult and a great deal of time is required to manufacture the tool, and at the same time, the holding force of the abrasive grains is drastically reduced and the generation of scratches cannot be suppressed.

  The present invention has been developed in order to solve such technical problems, that is, in order to consider defects in polishing processing of electronic devices made of composite materials such as magnetic heads. The present invention provides a manufacturing method that realizes production of a polishing tool for a device and reduces processing damage that affects device characteristics.

  Hereinafter, a method for producing a polishing tool in the present invention will be described in detail for each of the magnetic head device and the semiconductor device.

Example 1
The steps of FIGS. 1 to 3 will be described in detail. First, as a first step 5 in FIG. 1, a silicon wafer substrate 1 having a size of 5 inches (about 125 mm) was prepared for producing a polishing tool for an electronic device. The thickness was 5 mm, and polishing was performed only on one side using a polishing pad and colloidal silica slurry, and the surface roughness was adjusted to 1 nm or less with Ra. The silicon wafer substrate was set in the vacuum process chamber shown in FIG. 4, and after reducing the pressure to 1 × 10 ⁻⁴ Pa or less by a vacuum pump, Ar gas was introduced to about 10 to 20 mTorr.

  The subsequent processing is the second step 6 in FIG. First, Ar plasma was generated by applying a high-frequency voltage, and surface sputter etching was performed for several minutes with a self-bias of the base material by Ar ions at a high-frequency output of about 10 to 20 W. Next, the carbon target 9 and the pure Sn target 10 were set on the lower electrode. One target is used as a homogeneous material for the nanoparticle described later to stabilize the fixing of the nanoparticle, and the other Sn target material is used as a base material for the nanoparticle serving as abrasive grains.

First, in order to form the Sn film 3 having a constant film thickness of about several microns on the upper part of the substrate, sputtering film formation was performed by applying a high frequency voltage only to the Sn target. This region is referred to as an elastic region (FIG. 2).
Next, in order to efficiently fix the nano-particles 2 in the Sn film, the nano-particle introduction apparatus installed in the vacuum chamber is dispersed in a suitable solvent through a supply jet nozzle in the order of several micro to milligrams. The gas 8 is introduced into the plasma 8 intermittently in a state where it is likely to float.

  Nano-sized diamond particles were used as the nanoparticles for the magnetic head compatible tool. The nanoparticle 2 introduced into the plasma 8 is negatively charged by collision with electrons in the plasma and floats in the plasma. The plasma containing the nano fine particles is formed so as to cover the surface of the installed substrate.

  The plasma 8 is maintained by electric power supplied from the sputter electrodes 9 and 10. The power supply to the sputter electrodes 9 and 10 is stopped, and after a few nanoseconds to 1 millisecond, the pulse power source connected to the electrode on which the substrate 1 is placed has a width of 1 to several hundred milliseconds on the substrate surface. Apply a positive pulse potential.

  Electrons and ions in the plasma from which the power supply from the sputtering power source has been cut off collide with the wall surface of the chamber or the like, and negatively charged nanoparticles having a heavy mass and a slow speed remain in the space in the chamber. Since an electric field is generated by a positive potential applied to the substrate electrode, the nano fine particles are accelerated and attracted to the surface of the substrate 1 to be attached. After that, by restarting the power supply to the sputtering power source, the film is formed around the particles attached to the substrate 1 and the plasma 8 is generated again.

By repeating the above procedure an appropriate number of times during film formation, nanoparticles having a desired density could be fixed on the substrate 1. The layer containing the nano fine particles is referred to as an abrasive region, and the elastic region and the abrasive region are collectively referred to as an abrasive layer (FIG. 2).
In the above-described manufacturing method, the abrasive layer is separated into an abrasive region containing abrasive grains and an elastic region not containing abrasive grains, but only the abrasive layer containing nanoparticles is formed on the substrate from the beginning. However, it was possible to produce a polishing tool that could be expected to have the same effect in principle.

  In addition, as another method for efficiently fixing the nanoparticles 2 in the Sn film, an apparatus having a structure described below may be used. That is, in a nano-particle introduction device installed in a separate chamber having an electrically negative potential attached to the main vacuum chamber, in a state of several micro to milligrams through a supply jet nozzle in a state dispersed in an appropriate solvent. You may introduce | transduce into a chamber intermittently in the state which is easy to carry out a gaseous-phase floating.

  In the chamber, plasma is generated by electrons supplied from a fibrament for plasma excitation. Nanoparticles 2 introduced into the plasma are negatively charged by collision with electrons in the plasma and float in the plasma. The chamber is provided with two grid electrodes between the main chamber, the grid electrode on the chamber side can be given the same potential as the chamber, and the other grid can be given a positive potential to the chamber by a variable voltage power supply. The chamber itself is at a negative potential by the power source.

  When a potential is applied between the grids by the power source, the electrons and nanoparticles in the plasma 8 are accelerated by the electric field between the grids and introduced from the chamber into the main chamber. There is a magnet near the grid, and a magnetic field perpendicular to the traveling direction of electrons and nanoparticles is generated. At this time, although the path of the electron is bent by the magnetic field, the electron cannot travel straight, but the heavy nanoparticle travels straight and further accelerates due to the electric field formed by the potential difference with the chamber and reaches the surface of the substrate 1 with high energy. Even in such a system, the same effect as that of the apparatus shown in FIG. 4 can be expected.

  Subsequently, in the vacuum chamber, plasma etching was performed under relatively mild conditions using the introduced Ar gas (0 to −700 V) using the self-bias of the substrate (third step). This purpose was carried out in order to project a certain amount of nano-particles 2 fixed inside the base material from the surface of the base material. In order to make it close to the state of a conventional tool, the surface of the base material was protruded with about 1/3 of the particle size of the nanoparticle as a guide.

  The surface state of the polishing tool thus produced was evaluated. In order to evaluate the size and density of the nano fine particles, the measurement was performed with a secondary electron image of an electron microscope S5000 manufactured by Hitachi, Ltd. at a measurement magnification of 1 to 50,000 times. Furthermore, for the evaluation of the surface roughness of the tool, a silicon single crystal probe having a tip diameter of 10 nm was used with an atomic force microscope (AFM) Nanoscope IIIa, D3100 manufactured by Digital Instruments (currently Veeco). Detailed evaluation results are shown in FIG.

  The polishing tool thus produced was used to evaluate polishing of a magnetic head that is one of electronic devices. A magnetic head to be a polishing sample was held on a jig via a polyurethane elastic body and processed while being pressed against each polishing platen with a constant load within a range of 10 to 100 g weight. The number of rotations of the polishing tool was approximately 10 rpm or less. In addition, paraffinic hydrocarbon oil was used as the lubricant (finishing liquid), and the processing amount was about 30 nm or more.

The above-described atomic force microscope (AFM) was used for evaluation of the surface roughness after processing. For the surface roughness, the part with the smallest hardness on the magnetic element part (for example, the upper shield part) was evaluated with a measurement area of 1 × 6 μm ² . The polishing efficiency was evaluated by measuring the resistance value of the magnetic element before and after processing and converting it to the processing amount. As shown in FIG. 5, excellent results were obtained in both surface roughness and polishing efficiency.

(Example 2)
Next, as a semiconductor device, Cu removal polishing in a so-called metal wiring process (Cu damascene) was performed. In semiconductor devices such as logic and DRAM, conversion to Cu wiring is being promoted in order to cope with problems of wiring delay and electromigration caused by miniaturization. Since this Cu wiring is difficult to dry etch, Cu is embedded in a wiring groove formed in the insulating film, and excess Cu is polished and removed.

  Currently, polishing and removal of Cu damascene wiring is performed by CMP. However, in CMP, it is difficult to use a slurry, which is a mixture of a chemical solution and abrasive grains, high environmental load, and stable use of the slurry. Scratches caused by anything are a problem.

First, the silicon tool was used as the target material 9 in the same manner as in Example 1 for manufacturing the polishing tool. In addition, SiO ₂ particles having a particle size of about 30 nm were used as the nano-particles serving as abrasive grains, and fixing was performed in the Sn base material as one target material. The tool surface after fabrication was evaluated in the same manner as described above using an electron microscope S5000 manufactured by Hitachi, Ltd. and an atomic force microscope (AFM) Nanoscope IIIa, D3100 manufactured by Digital Instrument, USA. The evaluation results are shown in FIG.

As a Cu wiring device to be polished, a Si substrate with a Cu wiring pattern film was prepared. A SiO ₂ film, a TaN film, and a Cu film were formed on the Si (100) with a constant film thickness. Further, a wiring having a line width of several microns to 100 microns was formed on the SiO ₂ film on the substrate, and a Cu thin film layer was formed thereon by sputtering film formation and electrolytic plating. This substrate was cut into a 10 mm square and used for polishing. Regarding the polishing conditions, the number of revolutions of the polishing tool was substantially the same as that of the magnetic head of Example 1, and the load during polishing was adjusted in the range of 100 to 1000 g weight.

Moreover, at the time of a process, it grind | polished while supplying the aqueous solution which adjusted to weak alkalinity and added the benzotriazole for preventing the corrosion of Cu surface. After polishing, the surface roughness on the Cu wiring was evaluated with the above-mentioned atomic force microscope in the area range of 2 μm ² . The evaluation results are shown in FIG. Compared with CMP polishing using a conventional slurry, a deep scratch was not generated and smooth processing was performed.

Moreover, as a sputter target material for forming the first plasma, it was possible to produce with a material selected from any of C, Si, SiO ₂ , Sn and Sn-based alloys, Al, and Cu.

It is a figure which shows the basic process of grinding tool manufacture by this invention. It is a figure which shows the process and tool state of abrasive tool preparation of this invention. It is a figure which shows the process and tool state of abrasive tool preparation of this invention. It is a vacuum process apparatus in the present invention. It is an evaluation result in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Nanoparticle, 3 ... Base material, 4 ... 1st process, 5 ... 2nd process, 6 ... 3rd process, 7 ... Plasma, 8 ... Carbon, silicon target, 9 ... Sn target

Claims (9)

  A substrate polishing step for smoothing the substrate surface; a step of forming a polishing abrasive layer for polishing the surface of the electronic device on the substrate; and a method for causing abrasive grains to protrude from the surface of the abrasive layer. A polishing tool manufacturing method comprising a surface treatment step.   2. The method for manufacturing a polishing tool according to claim 1, wherein the abrasive layer forming step forms an abrasive region on the elastic region after forming an elastic region on the substrate.   3. The elastic region according to claim 2, wherein the elastic region is formed using a first plasma covering the surface of the substrate, and the abrasive region is formed by further supplying nanoparticles to the first plasma. A method for manufacturing a polishing tool.   2. The method for manufacturing a polishing tool according to claim 1, wherein the abrasive grain layer forming step is performed by supplying a first plasma containing nanoparticles to cover the surface of the substrate.   2. The method for manufacturing a polishing tool according to claim 1, wherein the surface treatment step is an etching treatment using second plasma on the surface of the abrasive layer. 4. The polishing tool according to claim 3, wherein the first plasma is a sputter plasma using a material selected from any of C, Si, SiO ₂ , Sn, a Sn-based alloy, Al, and Cu. Production method. _{2. The} method for manufacturing a polishing tool according to claim 1, wherein the abrasive grains are nano-particles made of diamond or SiO2.   8. The method for producing a polishing tool according to claim 7, wherein the nano fine particles have a diameter of 10 to 50 nm. 4. The method for manufacturing a polishing tool according to claim 3, wherein the nano fine particles are negatively charged by the first plasma.

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